Nonlinear Frequency Conversion of Photons for Quantum Networks

  • Thomas Wright

Student thesis: Doctoral ThesisPhD


Quantum networks provide a realistic framework through which large-scale quantum-information processing may be achieved. Underpinning the network approach is the establishment of quantum interconnects between nodes which facilitate the distribution of entanglement. To this end, recent and ongoing advances in the generation and manipulation of quantum states of light are of particular benefit. By employing existing optical-fibre infrastructure, light may be harnessed to transmit high-bandwidth quantum signals over vast distances. This is possible as photons will not ordinarily interact with each other and transmission at telecommunication wavelengths in the infrared minimises loss in fibre. However, many candidate quantum nodes operate at optical frequencies which are inherently lossy in optical fibre. Frequency conversion of single-photon states to low-loss telecommunication wavelengths is therefore key to the successful development of information-processing networks with dependable quantum interconnects.
The research described within this thesis concerns the frequency conversion of light between emission wavelengths of Sr+ ions and the telecommunication C band, addressing frequency conversion requirements of a planned quantum network under development by the UK’s Networked Quantum Information Technology Hub. Two conversion schemes are presented, each addressing emission lines located within different spectral regions. The first interface is based on second-order nonlinear processes in a bespoke custom-poled crystal and is used to demonstrate bi-directional single-photon-level conversion between 422 nm and the telecommunication C band. This frequency shift is unusually large and demonstrates a step forward in the capability to establish direct connections between the blue and UV, and telecommunication wavelengths. The second interface is enacted through a resource-efficient FWM scheme which permits the use of a single pulsed laser system. We demonstrate bidirectional frequency conversion between 1092 nm and the C band.
Date of Award22 Jul 2020
Original languageEnglish
Awarding Institution
  • University of Bath
SupervisorAndriy Gorbach (Supervisor) & Peter Mosley (Supervisor)

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